1. Field of the Invention
The present invention relates to a buckle apparatus for use in a seat belt system, into which a tongue plate is inserted for engagement therewith.
2. Description of the Related Art
In buckle apparatus for use in seat belt systems, there is a buckle apparatus having a so-called locking bar structure in which a lock plate for engaging a tongue plate is moved in a direction intersecting a tongue plate insertion direction and a tongue plate removal direction so as to engage the tongue plate.
In the buckle apparatus having the locking bar structure, there is provided a lock pin for holding the lock plate in a tongue plate engaging state where the lock plate engages the tongue plate. The lock pin is provided to be movable between a locked position where the lock pin holds the lock plate in the tongue plate engaging state, and a release position where the lock plate can be released from the tongue engaging state. When the lock pin is positioned at the locked position, the lock plate is held in the tongue plate engaging state, resulting in a locked condition. On the other hand, when the lock pin is positioned at the release position, the lock plate can serve to release the tongue plate engaging state.
The lock pin is urged by a spring in a direction of the locked position. That is, when the lock pin is positioned at the locked position for holding the lock plate in the tongue plate engaging state, the lock pin is urged by the spring so as to be held in the locked position. Accordingly, it is possible to hold the lock pin in the locked position without inadvertently releasing the tongue plate engaging state of the lock plate.
In order to release the engagement of the tongue plate by the lock plate, a release button is pressed against the urging forces of a return spring for urging the release button and a spring for urging the lock pin so as to forcedly move the lock pin from the locked position to the release position. Thus, the lock plate releases the tongue plate engaging state so as to remove the tongue plate from the buckle apparatus.
In the buckle apparatus having the locking bar structure as set forth above, there is an advantage in that enhanced secureness can be obtained between the tongue plate and the buckle apparatus, resulting in reliable engagement.
The lock pin is moved in the same direction from the locked position to the release position (i.e., a spring urging direction) as the release button is pressed into. Hence, in order to block movement of the lock pin due to an inertial force, the urging force of the spring for urging the lock pin is simply increased, or additional spring is required so as to enhance the holding force of the lock pin. In these cases, however, a stronger operating force is required for pressing the release button to move the lock pin to the release position so as to release the engagement.